On-line gaming is a field that is becoming more popular in an on-line cultural industry in recent years because of the development of networks and computer technology. Users have required various kinds of online games as the online games have developed, and very various categories of online games are currently serviced. Most online games presently serviced provide characters. The users use their terminals to access a game server, select a character provided by an online game, and control the character to enjoy the game. In the online game, there are characters that are provided without cost, and there are characters that the user must buy by using game points. When the user possesses a plurality of characters, he may alternately change a plurality of characters and may play a game. Among the online games providing a character, there is a game for the user to possess a team including a plurality of characters, individually scout, hire, or contract a plurality of respective characters configuring the team, and manage the team. The character usable in the game may be provided without a limit of period to the user, and depending on the kind of game, the character usage period may be restricted, a character usage fee may be paid again through a renewal when the usage period has expired, and the usage period of the corresponding character may be extended. One of such character providing games may provide special characters with capability points that are different from other characters so as to add users' interest to the game. The special character may be set to have capability points that are greater than those of a general character or have a special skill that is not assigned to other characters. Depending on the games, a characteristic of the special character may be realized not by a difference of capability points or skills but by a simple difference of character shapes. In the special character providing game, a method for a user to acquire a special character must be provided in a serious manner. When it is very easy for the user to acquire the special character, the number of users possessing the special character are increased. A scarcity value of the special character is then worsened and the users lose interest in the special character. On the contrary, when it is very difficult for the user to acquire the special character, most users except some users may abandon attempts at acquisition of the special character. Therefore, in consideration of an appropriate level for the user to feel interested, the game provider needs to allow the user to acquire the special character. The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.